Diffusion transfer color processes and products and compositions useful therein

ABSTRACT

Dye developer diffusion transfer processes are disclosed utilizing 6-alkylamino purines, preferably in combination with a silver halide solvent. In particularly useful embodiments, processing is effected in the presence also of a uracil and bis( Beta -aminoethyl)-sulfide.

United States Patent [191 Land et al. Jan. 15, 1974 DIFFUSION TRANSFER COLOR PROCESSES AND PRODUCTS AND [56] References Cited COMPOSITIONS USEFUL THEREIN UNITED STATES PATENTS [75] Inventors: Edwin H. Land, Cambridge; Stanley 2,857,276 10/1958 Land et al 96/29 R M. Bloom, Waban; Howard G. Rogers, Weston, all of Mass. Prima ExaminerNorman G. Torchin U E Alf T S P Assistant xaminer onso uro mo [73] Assignee. {gist-old Corporation, Cambridge, Attorney stanley H. Mervis et a.

[22] Filed; Dec. 23, 1971 57 CT [2]] App]. No.: 211,718 Dye developer diffusion transfer processes are disclosed utilizing 6-alkylamino purines, preferably in combination with a silver halide solvent. In particu- 5 Cl 96/3 gs 2 45 larly useful embodiments, Processing is effected in the [51] Int Cl Gosc 1/34 G030 5/54 6 7/00 presence also of a uracil and bis-(B'aminoethyU- [58] sulficm Field of Search 96/109, 66 R, 61 M, 96/29 D, 3, 77

48 Claims, No Drawings DIFFUSION TRANSFER COLOR PROCESSES AND PRODUCTS AND COMPOSITIONS USEFUL TI-IEREIN This invention is concerned with color photography and, more particularly, with photographic processes which provide diffusion transfer color images.

U. S. Pat. No. 2,983,606 issued May 9, 1961 to Howard G. Rogers, discloses photographic processes employing dye developers and, in particular, the formation of diffusion transfer color images by the use of dye developers. Diffusion transfer processes employing dye developers have been described in a plurality of patents.

The present invention is concerned with the use of 6-alkylamino purines in such processes.

The primary object of this invention is to provide novel photographic processes wherein an exposed silver halide emulsion is developed in the presence of a dye developer and a 6-alkylamino purine.

A further object of this invention is to provide diffu sion transfer color processes employing dye developers wherein maximum density is better maintained when the process is performed at temperatures above room temperature.

Other objects of this invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the product possessing the features, properties and the relation of components and the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims. 1

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description.

This invention is particularly directed to photographic processes wherein the desired image is obtained by processing an exposed photosensitive material, preferably silver halide, with a processing composition distributed between two sheet-like elements, one of said elements including said photosensitive material. The processing composition is so applied and confined within and between the two sheet-like elements as not to contact or wet outer surfaces of the superposed elements, thus providing a film unit or film packet whose external surfaces are dry. The processing composition may be viscous or nonviscous, and preferably is distributed from a single-use rupturable container; such pressure rupturable processing containers are frequently referred to as pods. The final image may be monochrome or multicolor.

As noted above, U. S. Pat. No. 2,983,606 described diffusion transfer color processes employing dye developers, i.e., a compound which is both a silver halide developing agent and a dye. A photosensitive element containing a dye developer and a silver halide emulsion may be exposed and wetted by a liquid processing composition, for example, by immersion, coating, spraying, flowing, etc., in the dark, and the exposed photosensitive element superposed prior to, during, or after wetting, on a sheetlike support element which may be utilized as an image-receiving element. In a preferred embodiment, the liquid processing composition is applied to the photosensitive element in a substantially uniform layer as the photosensitive element is brought into superposed relationship with the image-receiving layer. The liquid processing composition, positioned intermediate the photosensitive element and the imagereceiving layer, permeates the emulsion to initiate development of the latent image contained therein. The dye developer is immobilized or precipitated in exposed areas as a consequence of the development of the latent image. This immobilization is apparently, at least in part, due to a change in the solubility characteristics of the dye developer upon oxidation and especially as regards its solubility in alkaline solutions. It may also be due in part to a tanning effect on the emulsion by oxidized developing agent, and in part to a localized exhaustion of alkali as a result of development. In unexposed and partially exposed areas of the emulsion, the dye developer is unreacted and diffusible and thus provides an imagewise distribution of unoxidized dye developer, diffusible in the liquid processing composition, as a function of the point-to-point degree of exposure of the silver halide emulsion. At least part of this imagewise distribution of unoxidized dye developer is transferred, by imbibition, to a superposed imagereceiving layer or element, said transfer substantially excluding oxidized dye developer. The image-receiving layer receives a depthwise diffusion, from the developed emulsion, of unoxidized dye developer without appreciably disturbing the imagewise distribution thereof to provide a reversed or positive color image of the developed image. The image-receiving element may contain agents adapted to mordant or otherwise fix the diffused, unoxidized dye developer. If the color of the transferred dye developer is affected by changes in the pH of the image-receiving element, this pH may be adjusted in accordance with well-known techniques to provide a pH affording the desired color. In the preferred embodiments of said U.S. Pat. No. 2,983,606 and in the commercial applications thereof, the desired positive image is revealed by separating the imagereceiving layer from the photosensitive element at the end of a suitable imbibition period. Alternatively, as also disclosed in said U. S. Pat. No. 2,983,606, the image-receiving layer need not be separated from its superposed contact with the photosensitive element, subsequent to transfer image formation, if the support for the image-receiving layer, as well as any other layers intermediate said support and image-receiving layer, is transparent and a processing composition containing a substance, e.g., a white pigment, effective to mask the developed silver halide emulsion or emulsions is applied between the image-receiving layer and said silver halide emulsion or emulsions.

Dye developers, as noted above, are compounds which contain, in the same molecule, both the chromophoric system of a dye and also a silver halide developing function. By a silver halide developing function" is meant a grouping adapted to develop exposed silver halide. A preferred silver halide development function is a hydroquinonyl group. Other suitable developing functions include ortho-dihydroxyphenyl and orthoand para-amino substituted hydroxyphenyl groups. In general, the development function includes a benzenoid developing function, that is, an aromatic developing group which forms quinonoid or quinone substances when oxidized.

Multicolor images may be obtained using dye developers in diffusion transfer processes by several techniques. One such technique contemplates obtaining multicolor transfer images utilizing dye developers by employment of an integral multilayer photosensitive element, such as is disclosed in the aforementioned U. S. Pat. No. 2,983,606, and particularly with reference to P16. 9 of the patent's drawing, and also in U. S. Pat. No. 3,345,163 issued Oct. 3, 1967 to Edwin H. Land and Howard G. Rogers, wherein at least two selectively sensitized photosensitive strata, superposed on a single support, are processed, simultaneously and without separation, with a single common image-receiving layer. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide emulsion stratum and a blue sensitive silver halide emulsion stratum, said emulsions having associated therewith, respectively, for example, a cyan dye developer, a magenta dye developer and a yellow dye developer. The dye developer may be utilized in the silver halide emulsion stratum, for example in the form of particles, or it may be disposed in a stratum behind the appropriate silver halide emulsion strata. Each set of silver halide emulsion and associated dye developer strata are disclosed to be optionally separated from other sets by suitable interlayers, for example, by a layer or stratum of gelatin or polyvinyl alcohol. In certain instances, it may be desirable to incorporate a yellow filter in front of the green-sensitive emulsion and such yellow filter may be incorporated in an interlayer. However, where desirable, a yellow dye developer of the appropriate spectral characteristics and present in a state capable of functioning as a yellow filter may be so employed and a separate yellow filter omitted.

ability to provide colors that are useful in carrying out subtractive color photography, that is, the previously mentioned cyan, magenta and yellow. The dye developers employed may be incorporated in the respective silver halide emulsion or, in the preferred embodiment, in a separate layer behind the respective 'silver halide emulsion. Specifically, the dye developer may, for example, be in a coating or layer behind the respective silver halide emulsion and such a layer of dye developer may be applied by use of a coating solution containing the respective dye developer distributed, in a concentration calculated to give the desired coverage of dye developer per unit area, in a film-forming natural, or synthetic, polymer, for example, gelatin, polyvinyl alcohol, and the like, adapted to be permeated by the chosen diffusion transfer fluid processing composition. As examples of materials for use as the imagereceiving layer, mention may be made of solution dyeable polymers such as nylons as, for example, N- methoxymethyl polyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or without plasticizers; cellulose acetate with filler as, for example, one-half cellulose acetate and one-half oleic acid; gelatin; and other materials of a similar nature. Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4- vinylpyridine, as disclosed in U.S. Pat. No. 3,148,061, issued Sept. 8, 1964. 7' As disclosed in the previously cited patents, the liquid processing composition referred to for effecting multicolor diffusion transfer processes comprises at least an aqueous solution of an alkaline material, for

example, sodium hydroxide, potassium hydroxide, and the like, and preferably possessing a pH in excess of 12, and most preferably includes a viscosity-increasing compound constituting a film-forming material of the type which, when the composition is spread and dried, forms a relatively firm and relatively stable film. The preferred film-forming materials disclosed comprise high molecular weight polymers such as polymeric, water-soluble ethers which are inert to an alkaline solution such as, for example, a hydroxyethyl cellulose or sodium carboxymethyl cellulose. Additionally, filmforming materials or thickening agents whose ability to increase viscosity is substantially unaffected if left in solution for a long period of time are also disclosed to be capable of utilization. As stated, the film-forming material is preferably contained in the processing composition in such suitable quantities as to impart to the composition a viscosity in excess of cps. at a temperature of approximately 24 C. and preferably in the order of 100,000 cps. to 200,000 cps. at that temperature.

U. S. Pat. Nos. 3,415,644, 3,415,645 and 3,415,646, all issued Dec. 10, 1968 in the name of Edwin H. Land, disclose and claim photographic products and processes wherein a photosensitive element and an imagereceiving element are maintained in fixed relationship prior to exposure, and this relationship is maintained as a laminate after processing and image formation. In these processes, the final image is viewed through a transparent (support) element against a reflecting, i.e., white background. In a particularly useful embodiment, photoexposure is made through said transparent element and application of the processing composition provides a layer of light-reflecting material to provide a white background. The light-reflecting material (referred to in said patents and applications as an opacifying agent) is preferably titanium dioxide, and it also performs an opacifying function, i.e., it is effective to mask the developed silver halide emulsions so that the transfer image may be viewed without interference therefrom, and it also acts to protect the photoexposed silver halide emulsions from post-exposure fogging by light passing through said transparent layer if the photoexposed film unit is removed from the camera before image-formation is completed.

The copending application of Edwin H. Land, Ser. No. 101,968, filed Dec. 28, 1970 (now U. S. Pat. No. 3,647,437 issued Mar. 7, 1972), is concerned with improvements in the above-mentioned processes, and discloses the provision of light-absorbing materials to permit such processes to be performed outside of the camera in which photoexposure is effected and under much more intense ambient light conditions. A lightabsorbing material or reagent, preferably a dye, is provided so positioned and/or constituted as not to interfere with photoexposure but so positioned between the photoexposed silver halide emulsions and the transparent support during processing after photoexposure as to absorb light which otherwise might fog the photoexposed emulsions. Furthermore, the light-absorbing material is so positioned and/or constituted after processing as not to interfere with viewing the desired image shortly after said image has been formed. In the preferred embodiments, the light-absorbing material, also sometimes referred to herein as an optical filter agent, is initially contained in the processing composition together with a light-reflecting material, e.g., titanium dioxide. The concentration of the light-absorbing dye is selected to pfovide the light transmission opacity required to perform the particular process under the selected light conditions.

in a particularly useful embodiment, the lightabsorbing dye is highly colored at the pH of the processing composition, e.g.l, 13-14, but is substantially non-absorbing of visible light at a lower pH, e.g., less than -12. This pH reduction may be effected by an acid-reacting reagent appropriately positioned in the film unit, e.g., in a layer between the transparent support and the image-receiving layer.

For convenience, the disclosure of said Ser. No. 101,968 is hereby specifically incorporated herein.

It has now been found that such dye developer color processes may be improved by effecting development in the presence of a 6-alkylamino purine of the formula:

Where the alkyl group isa simple alkyl group, better results are generally obtained when the alkyl group contains more than one or two carbons. As will be apparent from the above, the alkyl group may be substituted, e.g., by halogen, alkoxy, etc.

The 6-alkylamino purine(s) may be initially positioned in the processing composition or in a layer of the element containing the silver halide emulsion(s) or the image-receiving layer. Especially good results have been obtained by incorporating the 6-alkylamino purine in the alkaline processing composition, and they have been found to be stable in strongly alkaline solutions for extended periods. This embodiment permits the 6-alkylamino purine to be available immediately after application of the processing composition. If, on the other hand, a delay is desired in the availability of the 6-alkylamino purine, it may be positioned in a layer of the film unit, it being understood that larger quantities of the 6-alkylamino purine may be required in such embodiments. Especially good results have been obtained when the o-alkylamino purine is incorporated in the processing composition at a concentration of about 0.01 to 1.0 percent by weight.

The fi-alkylamino purines have been found to be extremely effective in maintaining maximum dye density in dye developer transfer images when processing is conducted at temperatures above room temperature and especially at temperatures above 75 F. In addition, the use of a -alkyl-amino purine has been found effective in maintaining transfer image density in the absence of a development restrainer or arrestor, such as l-phenyl-5-mercaptotetrazole, in the image-receiving element. Of special significance is the fact that the 6- alkylamino purine is free of sulfur. thereby totally avoiding the problem of desensitization present when EXAMPLE 5 A multicolor photosensitive element of the type described in the above-mentioned copending application Ser. No. 101,968 was prepared using, as the cyan, magenta and yellow dye developers (liHa HC-NH-OzS-Q HOO-OH N H2 \C.

KIJHa OH S0z-NHCH H0 magenta:

HO-CHr-CE: Q

NS03 N=N CH3 Ho-oH,--0H, N O

r\-H:O l O O i OH 1 (ll I OH yellow:

OC3H7 I110: (131110 CH=N l O O /C1\Hz0 O O OH C-CH:CH2

An image-receiving element was prepared by coating a transparent polyethylene terephthalate film base with the following layers:

1. a layer of the half butyl ester of poly-( ethylene maleic anhydride) at a coverage of about 2,400 mg./ft.

2. A graft copolymer o f a crylamide and diaceton e acrylamide on a polyvinyl alcohol backbone in a molar ratio of l:3.2:l at a coverage of about 800 mg/ftf to provide a polymeric spacer layer; and

3. a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of about 300 mg/ftF. The photosensitive element was exposed and a processing composition was distributed in a layer approximately 0.0032 inch thick between the exposed multicolor photosensitive element and the imagereceiving element. The processing composition was prepared by adding 100 mg. of 6-benzylamino purine to ID cc. of a base processing composition comprising:

Water 156 cc. Potassium hydroxide (85%) 22.] g. N-benzyl-a-picolinium bromide (50% solution in water) 6.4 g. N-phenethyl-a-picolinium bromide 0.8 g. Sodium carboxymethyl cellulose (Hercules Type 7H4F providing a viscosity of 3000 cps. at 1% in water at 25 C.) 4.9 g. Titanium dioxide 72 g. 6-methyl uracil 3.36 g. bis-(B-aminoethyl)-sulfide 0.24 g. Lithium nitrate 0.56 g.

r 3.0 g. O I Q H H l HOOC NHSOZ ieHtz on on c0011 HOOI K\ The resulting sandwich was processed (outside of a camera) and a multicolor transfer image was obtained, viewable through the transparent polyethylene terephthalate base against the layer of titanium dioxide without separating the superposed elements. Essentially full density was obtained after 1% to 2 minutes. The multicolor image exhibited good color separation, good color saturation (especially magenta) and clean whites. Maximum density was maintained very well when processing was effected at temperatures of F. and higher.

It will be noted that the specific processing composition described above included 6-methyl uracil and bis-(B-aminoethyl)-sulfide:

This combination has been found to be an unusual complexer of silver halide, and to provide a much more difficultly reducible complex than do conventional silver halide solvents such as sodium thiosulfate. This effect is readily demonstrable in Xenon are accelerated ageing tests with respect to photolytic reduction. in a similar comparison of density obtained using a silver receptive element containing silver precipitating agents, much less density was obtained with this unique combination. ()ther uracils, c.g., uracil and 5-methyl uracil, give similar results in combination with the bis-(fi-aminoethyl)-sulfide. lt is particularly striking that the use of this reagent combination does not interfere with the development of exposed silver halide. In view of the increased light stability of silver halide complexed by such reagent combinations, it will be readily apparent that they would be advantageously employed in non-diffusion transfer processes such as the so-called stabilization development process (wherein undeveloped silver halide is retained in the developed silver halide emulsion) and in monobath processes to obtain fixed or stabilized" silver images, whether negative or positive.

The image-receiving element may be prepared according to the disclosure of U. S. Pat. No. 3,362,819 issued Jan. 9, 1968 to Edwin H. Land and U. S. Pat. No. 3,455,686 issued July l5, 1968 to Leonard C. Farney, Howard G. Rogers and Richard W. Young.

As noted above, the 6-alkylamino purine may be initially disposed in a layer of the photosensitive element. It has been demonstrated, e.g., by imbibing an unexposed negative briefly in a solution of 6-benzylamino purine prior to exposure, that the silver halide is not desensitized and that maintenance of maximum density in hot" processed multicolor diffusion transfer images is achieved.

The amount of the -alkylamino purine to effectively maintain maximum density in dye developer diffusion transfer will vary as a function of the other reagents present. Thus, it has been found that if a silver halide solvent is not present, the concentration of 6- benzylamino purine may be only one-tenth of that required when a silver halide solvent is present. It will be readily apparent that the appropriate concentration may be readily determined by routine experimentation.

Development is advantageously effected in the presence of an onium compound, particularly a quaternary ammonium compound, in accordance with the processes' disclosed in U. S. Pat. No. 3,173,786 issued Mar. 16, 1965 to Milton Green and Howard G. Rogers. Quaternary ammonium compounds which form an active methylene compound in alkali are especially useful.

Development may be effected in the presence of a colorless auxiliary or accelerating developing agent,

such as a 3-pyrazolidone or a hydroquinone, such as 4'-methylphenylhydroquinone, which may be initially positioned in a layer of the photosensitive element or in the processing composition, in accordance with known techniques.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A photographic color process comprising exposing a photosensitive silver halide emulsion, and applying an alkaline processing composition to said exposed silver halide emulsion to effect development of exposed silver halide, said development being effected in the presence of a dye developer and a o-alkylamino purine of the formula:

wherein R is an alkyl group.

2. A photographic color process as defined in claim 1 wherein R is 3. A photographic color process as defined in claim 1 wherein R is 5. A photographic color process as defined in claim 1 wherein an imagewise distribution of unoxidized dye developer is formed in undeveloped areas of said silver halide emulsion as a function of said development, said process including the step of transferring by diffusion at least a portion of said imagewise distribution of unoxidized dye developer to an image-receiving layer in superposed relationship with said silver halide emulsion, thereby providing a positive diffusion transfer dye image.

6. A photographic color process as defined in claim 1 wherein the photosensitive element which is exposed comprises a blue-sensitive silver halide em ulsion having a yellow dye developer associated therewith, a greensensitive silver halide emulsion having a magenta dye developer associated therewith, and a red-sensitive silver halide emulsion having a cyan dye developer associated therewith, and said positive diffusion transfer dye image is a multicolor image.

7. Aphotographic color process as defined in claim 6 wherein said 6-alkylamino purine is initially present in said processing composition in a concentration of about 0.0l to 1.0 percent by weight.

8. A photographic processing composition comprising water, alkali, a silver halide developing agent and a o -alkylamino purine of the formula:

wherein R is an alkyl group.

9. A photographic processing composition as defined in claim S wherein said 6-alkylamino purine is present in said processing composition in a concentration of about 0.01 to 1.0 percent by weight.

10. A photographic processing composition as defined in claim 8 wherein R is 11. A photographic processing composition as defined in claim 8 wherein R is 14. A photographic processing composition as defined in claim 12 wherein R is 15. A photographic processing composition as de fined in claim 12 wherein R is 16. A photographic processing composition as defined in claim 12 including a silver halide developing agent.

17. A photographic processing composition as defined in claim 12 including a viscosity-increasing material.

18. A photographic processing composition as defined in claim 12 including a quaternary ammonium salt.

19. A photosensitive element comprising a support, a layer on said support containing a photosensitive silver halide emulsion, a layer on said support containing a dye developer, and a layer on said support containing a 6-alkylamino purine of the formula:

wherein R is an alkyl group.

20. A photosensitive element as defined in claim 19 including a blue-sensitive silver halide emulsion having a yellow dye developer associated therewith, a greensensitive silver halide emulsion having a magenta dye developer associated therewith, and a red-sensitive silver halide emulsion having a cyan dye developer associated therewith.

21. A photosensitive element as defined in claim 20 wherein said 6-alkylamino purine is contained in a layer over said blue-sensitive silver halide emulsion.

22. A photosensitive element as defined in claim 19 wherein R is 23. A photographic color process as defined in claim 1 wherein said development is effected at a temperature above 75 F.

24. A photographic color process as defined in claim wherein a layer containing titanium dioxide is positioned between said image-receiving layer and said silver halide emulsion whereby said positive dye image may be viewed without separating said image-receiving layer from said silver halide emulsion.

25. A photographic color process as defined in claim 24 wherein said titanium dioxide is initially present in said processing composition.

26. A photographic color process as defined in claim 1 wherein a silver halide solvent is also present.

27. A photographic color process as defined in claim 1 wherein said development is effected in the presence of a uracil.

28. A photographic color process as defined in claim 27 wherein said uracil is 5-methyl uracil.

29. A photographic color process as defined in claim I wherein said development is effected in the presence of S-methyl uracil and bis-(fi-aminoethyl)-sulfide.

30. A photographic processing composition comprising water, a uracil and bis-(B-aminoethyl)-sulfide.

31. A photographic processing composition as defined in claim 30 wherein said uracil is 6- methyl uracil.

32. A photographic processing 'coiripbs'iii'n"a'a fined in claim 30 including a silver halide developing agent.

33. in a photographic process wherein a silver halide emulsion is exposed and developed with a silver halide developing agent, the step of contacting undeveloped silver halide with a processing composition containing a uracil and bis-(B-aminoethyD-sulfide during or after development of said exposed silver halide emulsion.

34. The photographic process as defined in claim 33 wherein said uracil is 6-methyl uracil.

35. The photographic process as defined in claim 33 wherein said uracil and said bis-(B-aminoethyl)-sulfide are present in the same processing composition as said silver halide developing agent.

36. A photographic product for use in forming a color image by diffusion transfer, said product comprising, in combination, a photosensitive element, a rupturable container releasably holding a viscous, alkaline processing composition, and an image-receiving layer, said photosensitive element comprising a support carrying at least one photosensitive silver halide emulsion, each said silver halide emulsion having associated therewith a dye developer, said product also including a -alkylamino purimhe formula:

wherein R is an alkyl group, said 6-alkylamino purine being present in said processing composition or in a layer of said film unit.

37. A photographic product as defined in claim 36 wherein R is 38. A photographic product as defined in claim 36 wherein R is 39. A photographic product as defined in claim 36 wherein R is O CH:

40. A photographic product as defined in claim 36 wherein said photosensitive element comprises a bluesensitive silver halide emulsion having a yellow dye developer associated therewith, a green-sensitive silver halide emulsion having a magenta dye developer associated therewith, and a red-sensitive halide emulsion having a cyan dye developer associated therewith.

41. A photographic product as defined in claim 36 wherein said processing composition includes titanium dioxide dispersed therein.

42. A photographic product as defined in claim 36 wherein a silver halide solvent is also present.

43. A photographic product as defined in claim 42 wherein said silver halide solvent is a uracil.

44. A photographic product as defined in claim 43 wherein said uracil is S-methyl uracil.

45. A photographic product as defined in claim 43 wherein said uracil is 6-methyl uracil.

about 0.01 to 1.0 percent by weight.

48. A photographic product as defined in claim 36 wherein said image-receiving layer is carried on a transparent support. 

2. A photographic color process as defined in claim 1 wherein R is
 3. A photographic color process as defined in claim 1 wherein R is
 4. A photographic color process as defined in claim 1 wherein R is
 5. A photographic color process as defined in claim 1 wherein an imagewise distribution of unoxidized dye developer is formed in undeveloped areas of said silver halide emulsion as a function of said development, said process including the step of transferring by diffusion at least a portion of said imagewise distribution of unoxidized dye developer to an image-receiving layer in superposed relationship with said silver halide emulsion, thereby providing a positive diffusion transfer dye image.
 6. A photographic color process as defined in claim 1 wherein the photosensitive element which is exposed comprises a blue-sensitive silver halide emulsion having a yellow dye developer associated therewith, a green-sensitive silver halide emulsion having a magenta dye developer associated therewith, and a red-sensitive silver halide emulsion having a cyan dye developer associated therewith, and said positive diffusion transfer dye image is a multicolor image.
 7. A photographic color process as defined in claim 6 wherein said 6-alkylamino purine is initially present in said processing composition in a concentration of about 0.01 to 1.0 percent by weight.
 8. A photographic processing composition comprising water, alkali, a silver halide developing agent and a 6-alkylamino purine of the formula:
 9. A photographic processing composition as defined in claim 8 wherein said 6-alkylamino purine is present in said processing composition in a concentration of about 0.01 to 1.0 percent by weight.
 10. A photographic processing composition as defined in claim 8 wherein R is
 11. A photographic processing composition as defined in claim 8 wherein R is
 12. A photographic processing composition comprising water, alkali, a silver halide solvent and a 6-alkylamino purine of the formula:
 13. A photographic processing composition as defined in claim 12 wherein said 6-alkylamino purine is present in said processing composition in a concentration of about 0.01 to 1.0 percent by weight.
 14. A photographic processing composition as defined in claim 12 wherein R is
 15. A photographic processing composition as defined in claim 12 wherein R is
 16. A photographic processing composition as defined in claim 12 including a silver halide developing agent.
 17. A photographic processing composition as defined in claim 12 including a viscosity-increasing material.
 18. A photographic processing composition as defined in claim 12 including a quaternary ammonium salt.
 19. A photosensitive element comprising a support, a lAyer on said support containing a photosensitive silver halide emulsion, a layer on said support containing a dye developer, and a layer on said support containing a 6-alkylamino purine of the formula:
 20. A photosensitive element as defined in claim 19 including a blue-sensitive silver halide emulsion having a yellow dye developer associated therewith, a green-sensitive silver halide emulsion having a magenta dye developer associated therewith, and a red-sensitive silver halide emulsion having a cyan dye developer associated therewith.
 21. A photosensitive element as defined in claim 20 wherein said 6-alkylamino purine is contained in a layer over said blue-sensitive silver halide emulsion.
 22. A photosensitive element as defined in claim 19 wherein R is
 23. A photographic color process as defined in claim 1 wherein said development is effected at a temperature above 75* F.
 24. A photographic color process as defined in claim 5 wherein a layer containing titanium dioxide is positioned between said image-receiving layer and said silver halide emulsion whereby said positive dye image may be viewed without separating said image-receiving layer from said silver halide emulsion.
 25. A photographic color process as defined in claim 24 wherein said titanium dioxide is initially present in said processing composition.
 26. A photographic color process as defined in claim 1 wherein a silver halide solvent is also present.
 27. A photographic color process as defined in claim 1 wherein said development is effected in the presence of a uracil.
 28. A photographic color process as defined in claim 27 wherein said uracil is 5-methyl uracil.
 29. A photographic color process as defined in claim 1 wherein said development is effected in the presence of 5-methyl uracil and bis-( Beta -aminoethyl)-sulfide.
 30. A photographic processing composition comprising water, a uracil and bis-( Beta -aminoethyl)-sulfide.
 31. A photographic processing composition as defined in claim 30 wherein said uracil is 6-methyl uracil.
 32. A photographic processing composition as defined in claim 30 including a silver halide developing agent.
 33. In a photographic process wherein a silver halide emulsion is exposed and developed with a silver halide developing agent, the step of contacting undeveloped silver halide with a processing composition containing a uracil and bis-( Beta -aminoethyl)-sulfide during or after development of said exposed silver halide emulsion.
 34. The photographic process as defined in claim 33 wherein said uracil is 6-methyl uracil.
 35. The photographic process as defined in claim 33 wherein said uracil and said bis-( Beta -aminoethyl)-sulfide are present in the same processing composition as said silver halide developing agent.
 36. A photographic product for use in forming a color image by diffusion transfer, said product comprising, in combination, a photosensitive element, a rupturable container releasably holding a viscous, alkaline processing composition, and an image-receiving layer, said photosensitive element comprising a support carrying at least one photosensitive silver halide emulsion, each said silver halide emulsion having associated therewith a dye developer, said product also including a 6-alkylamino purine of the formula:
 37. A photographic product as defined in claim 36 wherein R is
 38. A photographic product as defined in claim 36 wherein R is
 39. A photographic product as defined in claim 36 wherein R is
 40. A photographic product as defined in claim 36 wherein said photosensitive element comprises a blue-sensitive silver halide emulsion having a yellow dye developer associated therewith, a green-sensitive silver halide Emulsion having a magenta dye developer associated therewith, and a red-sensitive silver halide emulsion having a cyan dye developer associated therewith.
 41. A photographic product as defined in claim 36 wherein said processing composition includes titanium dioxide dispersed therein.
 42. A photographic product as defined in claim 36 wherein a silver halide solvent is also present.
 43. A photographic product as defined in claim 42 wherein said silver halide solvent is a uracil.
 44. A photographic product as defined in claim 43 wherein said uracil is 5-methyl uracil.
 45. A photographic product as defined in claim 43 wherein said uracil is 6-methyl uracil.
 46. A photographic product as defined in claim 43 wherein bis-( Beta -aminoethyl)-sulfide is also present.
 47. A photographic product as defined in claim 36 wherein said 6-alkylamino purine is initially present in said processing composition in a concentration of about 0.01 to 1.0 percent by weight.
 48. A photographic product as defined in claim 36 wherein said image-receiving layer is carried on a transparent support. 